Re: Ammeter Configurations

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Ozone Junkie" <OzoneJunkie-at-gmail-dot-com> 

G'Day Again,

The problem is in getting a 0-250 full scale AC voltmeter.  I have
scoured all my usual parts sources here in Aus, and can't find any AC
meters for affordable prices.  The coil is only a 12/30 (360VA) but i
want to be able to read upto about 6A (1.44kVA).  From what I thought,
there is no point in trying to build a small current transformer for
this small amount.

That is why I am trying to use the smaller, cheaper, easier to get DC
versions.  I was originally using 0.1r across a digital panel meter,
but it has died a rapid death.  I am trying to avoid using external
DMM's for a 'neatness' factor, but I am thinking that that might be
the only way.

Tristan



On Mon, 04 Oct 2004 19:06:38 -0600, Tesla list <tesla-at-pupman-dot-com> wrote:
 > Original poster: "Dr. Resonance" <resonance-at-jvlnet-dot-com>
 >
 > Tristin:
 >
 > This is how we do it.  Since the coil is powered by an AC transformer, just
 > use a 0-250 full scale AC voltmeter that the dial faceplate is re-calibrated
 > in 0-16,363 Volts.  We usually round this off to 16,500 VAC full scale.
 >
 > In normal operation the meter will read 14,400 Volts at 220 Volts input.
 > This is the Erms potential and the cap will fire at 1.414 * Erms (actually
 > this depends on your sparkgap setting for exact value).
 >
 > A cheap easy way to accomplish the task and no messy HV dividers necessary.
 > Also, very accurate for TC work requirements.
 >
 > We also do this with NSTs, just using a different value.  The math is a
 > simple ratio proportion:
 >
 > X = (250 V. * 14.4 kV) / 220 VAC        X = 16.353 kV fullscale reading for
 > a pole xmfr
 >
 > or X = (150 VAC * 12 kV) / 120 VAC    X = 15 kV fullscale for a 12 kV NST
 >
 > Dr. Resonance
 >
 > Resonance Research Corporation
 > E11870 Shadylane Rd.
 > Baraboo   WI   53913
 >
 >
<SNIP >